3rd Generation Nest kicks on AC and Furnace

[ChrisJMeng]

Hey everyone,

Long Story: I bought a new house about 2 years ago and have been running into some HVAC issues. Its an AC with Gas Furnace that includes a Whole house Humidifier. For whatever reason the Furnace will randomly kick on with the AC. It tends to be during dusk when the outside cools off but the house can be hot. Or like today. Low 60s and sunny and the AC kicked on because my sons room got to 73. Screen goes blue an everything. We originally thought it was the WHH because he WHH came with a smart humidistat so we removed the "Smart" and replaced it with an old models that just adjusts with humidity but should can kick on the fan. Still happened. So I completely disconnected the WHH. Still happened. Had 2 different companies come out and check and everything seems to be on the up and up. Then today it happened again. The only thing I can think is the Nest Controller but unfortunately its out of warranty.

Current Wiring  

Any help would be awesome!

[ChrisJMeng]

@CoolingWizard @Patrick_Caezza

[ChrisJMeng]

I did notice that the "Heat Source" is set to Electric but its a gas furnace. 

[sicsacol]

Hi @ChrisJMeng,

Thanks for reaching out to the community page. I'm sorry to hear your furnace randomly kicks on with the AC in your house. I understand that you've already contacted some technicians to check your system and the issue persists, I really appreciate your cooperation and your troubleshooting efforts. Don't worry, let's work together to get this fixed. To help me with that, I have a few questions:

• What type of Nest thermostat do you have? To check it, please visit the next article: How to tell which Nest thermostat you have.
• Are there any error messages on your Nest thermostat display? If so, what are they exactly?
• Have there been any recent changes or upgrades to your HVAC system?
• Have you experienced any power outages within the last few days or weeks?
• Does the issue happen on heating only, cooling only, or both?
• Please share a picture of your current wiring information. You can upload the picture by clicking on the "camera icon" before sending the reply.

Please answer these questions and add any other relevant information.

Cheers,
Jonathan 

[ChrisJMeng]

It's a gen 3

No errors. It has a blue screen that acts like the air is going.

No changes or power losses. 

Only happens on air, even when it's in cooling mode and not the cooling and heat mode

[ChrisJMeng]

 

[sicsacol]

Hi @ChrisJMeng,

Thanks for your reply.

Based on the picture, your wiring configuration seems to be good. However, since you’ve already contacted your HVAC technician to check your system and the issue persists, the team would like to learn more about this behavior. When you get a chance, please fill out this form and let us know when you’re finished. We’ll have someone reach out to you via email from there. Please make sure to add the link of this thread and your community username.

Let me know once you've submitted the form.

Sincerely,
Jonathan